Need to know how many Supervisors would be required for a 100 seat call centre or how many Customer service reps per 1 trainer.

No. of supervisors required for 100 seats should be around 7-8 (ratio of around 14-15 reps per team)
no of service reps per trainer can be better defined by ur training needs. a good ration is around 18 people per training class

I would tend to go for 12 agents to a supervisor/manager.
Training wise a typical class would be about 15.

I agree, the perfect supe:agent ratio is 1:12-15. However, many call centers run as high as 25+ agents per supervisor, which is considerably less expensive, but sacrifices quality. Most outsourcing contracts require an 1:18 ratio as a minimum.

The range for trainers is 1:15-25, factoring in ongoing training past new hire training. Quality Assurance staff runs usually 1:25-30, depending on the contract. However, easily 65% of our clients who run internal call centers don't even have a QA group (which is a no-no).

Brent